From Longman Dictionary of Contemporary Englishbe on the wrong track/tackbe on the wrong track/tackWRONG/INCORRECTto have the wrong idea about a situation so that you are unlikely to get the result you want → wrong
Examples from the Corpus
be on the wrong track/tack• He admitted that he had gotten us off on the wrong tack, and that we'd need to start again.• I feel that this advertising campaign is on completely the wrong tack.• I knew I was on the wrong track when the tall reeds broke to reveal the brown-bellied river. 